Accelerating a vehicle, decelerating the vehicle, or maintaining vehicle speed (i.e., neither accelerate nor decelerate the vehicle) are each generally accomplished through driver interaction with an accelerator pedal in a motor vehicle. In internal combustion engines, a vehicle drive train typically includes an engine coupled to a multiple-speed ratio transmission which in turn is coupled via a drive shaft and differential to a pair of driven wheels. The position of a throttle placed within an intake manifold of the engine is controlled to produce power for driving the wheels. The throttle is positioned by an electric motor under the control of an engine or powertrain control module (PCM) which also controls the operation of the engine and transmission. Additionally, the PCM controls conventional spark and fuel control devices that may be coupled to engine. The PCM typically operates based on a number of inputs including engine speed, vehicle speed, accelerator pedal position, and throttle position. These inputs are provided by various conventional sensors such as shaft speed sensors and throttle position sensors.
In general, the PCM activates the electric motor to position the throttle according to a desired throttle area determined in response to accelerator pedal position and various control functions, such as idle speed control, engine governor control, cruise control, and traction control. For example, a depression of the accelerator pedal results in a corresponding movement of a throttle valve by the electric motor that controls the opening and closing of the throttle valve. The degree of depression results in a movement of the throttle plate through a corresponding angle. These functions may be implemented using an electronic throttle control (ETC) which uses a simple pedal position to throttle position comparison based on pedal position sensors (PPSs) and throttle position sensors (TPSs), respectively. Typically, such control includes adjusting throttle valve position by controlled motor motion to provide appropriate restriction to an air passage into the engine. When the accelerator pedal is depressed by the driver, the angle of the throttle valve is increased by the throttle actuator. This allows more air into the engine and generally increases engine power.
The PCM may be responsive to any one of several factors used to formulate a current desired throttle position. For example, such factors may include inputs indicative of the engine operating conditions, an operator command from an accelerator pedal, or information from an active cruise control algorithm. Feedback may be provided to the PCM from a conventional throttle valve position sensor communicating a signal to the controller, the magnitude of which is related to the degree of opening of the throttle valve or plate.
In the past, ETC systems using throttle position sensors (TPSs), typically two TPSs, have generally relied upon a single reference and return for each TPS. For example, a 5 Volt reference, 5VA, is used as a reference and return for both TPS1 and PPS2, and a 5 Volt reference, 5VB, is used as a reference and return for both TPS2 and PPS1. In this example, a manifold absolute pressure (MAP) sensor had the same reference and return as the TPS2 sensor, namely the MAP sensor also used 5VB as a reference and return with TPS2.
One concern with ETC systems is failure mode response to account for safety considerations of vehicle operation. In the previous example, a loss of 5VA reference or return (or ground) results in a malfunction indicator lamp (MIL) activation and limited throttle authority (LTA) whereby the throttle can only be displaced to a limited degree, a loss of 5VB reference or return results in MIL activation and engine shutdown whereby fuel is shut-off, and a loss of MAP results in MIL activation and default throttle authority (DTA), also referred to as limp-home mode, whereby the throttle is parked. Additionally, conventional ETC systems have generally used a MAP sensor for sensing air pressure and deriving airflow when providing remedial actions. However, the automotive industry continually demands improvements to existing remedial actions of ETC to provide continued safety improvements while minimizing, maintaining, or decreasing overall cost of incorporating such improvements.
Accordingly, it is desirable to provide a throttle position sensor up-integrated electronic throttle control system having improved failure mode response. In addition, it is desirable to provide an electronic throttle control system using a mass airflow sensor and a manifold absolute pressure sensor that has improved failure mode response. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.